Process for treating liquid zinc amalgams



Patented Apr. 29, 1941 UNITED STATES PATENT OFFICE PROCESS FOR TREATINGLIQUID ZINC AMALG AMS Germany No Drawing. Application August-11, 1939,Serial No. 289,632. In Germany June 21, 1937 9 Claims.

The present invention relates to a process for maintaining the goodfiowability of liquid zinc amalgams.

For the technical working with zinc amalgams it is necessary, if desiredto cause the amalgam to circulate, to pass it through tubes and exactlyto proportion its proportions. such steps and the performance ofcontinuous processes in general require a good fluidity (i. e. mobility)of the zinc amalgam. Such good fluidity especially is also required whenpreparing the amalgams electrolytically. It has been attempted toproduce this desirable fluidity by working in an inert gas. especiallyin a nitrogen atmosphere so as to prevent the formation of oxide.

In accordance with the present invention the good fiowability of zincamalgams can be maintained in an especially advantageous manner. withcentainty and permanently, by bringing into contact the zinc amalgamswith solutions having the property of dissolving zinc oxide, preferablywith aqueous solutions and of such concentration that the zinc amalgamis practically not attacked. The working may be performed at ordinary orhigher temperatures. In most cases it is advantageous to cover theamalgam with solutions; amalgam, for instance, which has beenmanufactured in a horizontal cell as is used inthechlorinealkalielectrolysis, and which is passed back into the cycle from the cell tothe circulation pump by way of a return channel, is brought into contactI with solutions in such a way that the solvent is injected into thepumps and then is led back through a channel, whereupon the amalgam iscover d by the solutions. It is especially advantageous to use aoueousdilute hydrochloric or sulfuric acid solutions; for example normalhydrochloric acid solutions may be used, But it is also possible to usealkaline reacting solutions. as for instance. ammonia and ammoniumcarbonate solutions. Furthermore solutions may be used containing freechlorine. The dilute aoueous solutions used take up only such a smallquantity of zinc that it may be neglected when compared with the contentof zinc of the amalgams. Preferably the solution is passed over theamalgam in a slow stream, so that the solution is continuously renewed.It is also possible to use anhydrous, for instance ethereal andalcoholic solutions, for instance such solutions of hydrogen chloride orbromide. Amalgams already oxidized acquire good fluidity again whentreated with solutions in accordance with the process mentioned above.

The invention is further illustrated in the following examples:

Example 1 In one of the known amalgam cells, as generally used in theindustry for electrolyzing alkali metal chlorides, of a width of meterand a length of about 6 meters, mercury flowing at the bottom of thecell from one end to the other below the electrolyte serves as thecathode. The amalgam formed flows back from a considerably narrowerreturn channel to the other end, and is then fed by means of acirculating pump back into the cell proper, so that an interruptedcircuit of the mercury or amalgam respectively takes place. From theamalgam continuously circulating a part of the zinc amalgamcorresponding to the electrical current is permanently taken off andworked up in the desired manner, while at the other end continuously acorresponding quantity of fresh mercury is fed in.

In that part of the cell not passed by the current the amalgam isirrigated by a T 6 normal aqueous hydrochloric acid heated to 90 C. Theacid is injected for this purpose into the inner part of the circulatingpump when it overflows into the return channel; it then flows throughthe whole length of .the channel and leaves it at the other end throughan overflow. The speed of feeding amounts to 30-60 liters per hour. Thesuccess of this procedureis such a perfect one that after 3 months ofworking the amalgam is still as bright as it was before. This result isobtained without filling the apparatus with inert gases. The exclusionof oxygen has proved superfluous.

Example 2 the current a part is taken off and introduced together with asmall quantity of sulfuric acid into the circulating pump. The contentof sulfuric acid of the electrolyte thus introduced amounts to normal.After a few days in this case also the amalgam remains absolutelybright.

Example 3 In a trough, provided with a scoop apparatus and closedagainst the outer air a 5% amalgam heated up to C. flows forconcentration pur poses. Through the same trough flows a t-normalammonium carbonate solution cooled to +5 0., which is circulated by apump between this trough and a heat exchanger. By means of the scoopapparatus a kneadable solid amalgam with an average zinc content of 10%is drawn all while an abouty1 readily mobile amalgam flows away throughan overflow. The ammonium carbonate solution enrichenecl with zinc isremoved from time to time, about once a week, the ammonium carbonateregenerated by driving off with steam and introducing carbonic acid, andthe basic zinc carbonate resulting there from is obtained as aby-product.

Example 4 The working is performed as described in Example 1 while usinginstead of the hydrochloric acid the electrolyte running oil? from thatpart of the cell conducting the current and containing free chlorine.

Example 5 An apparatus for the distillation of zinc amalgam is fed froma cast-iron vessel in which a 5% zinc amalgam, heated to 75 C. iscovered by a 10% sodium hydroxide solution; the sodium hydroxidesolution is drawn oil from time to time and replaced by a fresh one.

Example 6 In front of a valve destined for measuring the zinc amalgam acylindrical vessel is located provided with a siphon delivery. Theamalgam present in the vessel is covered with water, through which apart of the chlorine gas evolved in the cell is slowly passed.

Example 7 In front of a valve destined for measuring the zinc amalgam acylindrical vessel lslocated provided with a siphon delivery. Theamalgam conwith 1 normal of liquid zinc amalgam which consists incovering the liquid zinc amalgam with aqueous solutions of substancescapable of dissolving zinc oxide and of such a concentration that thezinc amalgam is practically not attacked.

3. Process for maintaining the good fiowability of liquid zinc amalgamwhich consists in covtions of hydrochloric acid capable of dissolvingzinc oxide and of such a concentration that the zinc amalgam ispractically not attacked.

5. Process for maintaining the good flowability of liquid zinc amalgamwhich consists in covering the liquid zinc amalgam with basic reactingaqueous solutions of substances capable of dissolving zinc oxide and ofsuch a concentration that the zinc amalgam is practically not attacked.

6. Process for maintaining the good flowability of liquid zinc amalgamwhich consists in covering the liquid zinc amalgam with aqu oussolutions of ammonium carbonate capable of dissolving zinc oxide and ofsuch a concentration that the zinc amalgam is practically not attacked.

7. Process for maintaining the good flowability of liquid zinc amalgamwhich consists in covering the liquid zinc amalgam with organicsolutions of substances capable of dissolving zinc oxide and of such aconcentration that the zinc amalgam is practically not attacked.

8. Process for maintaining the good flowability of liquid zinc amalgamwhich consists in covering the liquid zinc amalgam with organic solu-'tions of an acid capable of dissolving zinc oxide and of such aconcentration that the zinc amalgam is practically not attacked.

9. Process for maintaining the good fiowability of liquid zinc amalgamwhich consists in covering the liquid zinc amalgam with an alcoholicsolution of hydrochloric acid capable of dissolving zinc oxide and ofsuch a concentration that the zinc amalgam is practically not attacked,

HERMANN WOLF. ERNST KUSS.

HANS HOHN. v FRITZ STIETZEL.

